Conservation groups are seeking Endangered Species Act protection for chinook salmon in the Klamath River running from Southern Oregon across Northern California.

The petition filed Thursday with the NOAA Fisheries Service says spring chinook that once were the most prized and numerous of the salmon returning each year to the Klamath are down to between 300 and 3,000 that survive to spawn each year.

Fall chinook are doing better.

If granted, protection would further complicate the tough decisions on sharing scarce water between fish and farms in the Klamath Basin, where coho salmon and two species of suckers already are protected.

The proposal comes as the U.S. Department of Interior studies whether to go through with a landmark agreement to remove four hydroelectric dams on the river to help salmon.